Tech Updates

Cold Mounting: Interference fits require even more care during installation because the bearing has a smaller bore or a larger outside diameter than the mating part. Bearings with relatively small interference fits can be press fit at room temperature by using a sleeve against the ring face.

Bearings are frequently mounted by striking the sleeve with a hammer, however, if available, use a mechanical or hydraulic press because it applies a more uniform force.

When mounting a non-separable bearing on a shaft and in a housing at the same time, use a pad that distributes the fitting pressure evenly over the inner and outer rings.

Heated Mounting: Bearings with large inner ring interference require a considerable amount of force to mount at room temperature. Mounting is facilitated by heating and thus expanding the inner ring.

The amount of heating required depends on the amount of interference and the shaft diameter.
If you are immersing bearings in hot oil, to avoid overheating, suspend the bearings inside the heating tank on a wire grid. Never bring bearings in direct contact with the heating element or bottom of the tank.

When using a hot plate to heat bearings, gaps between the inner ring and the abutment can be avoided by holding the inner ring against the shaft abutment during cooling.

It is essential to apply heat uniformly throughout the entire bearing. Do not use a torch to heat the inner ring during installation because it produces high localized heat. NTN bearings should never be heated above 248ºF.

Slack Adjuster Tip
ArvinMeritor offers the following tip for troubleshooting brakes:
Always troubleshoot brakes when the air chamber stroke exceeds the allowable limit. When you need to replace one automatic slack adjuster (ASA), replace all the ASAs on the same axle with components that meet the original specification.

Mismatched brands can result in uneven brake wear, unbalanced braking and poor brake performance.

Meritor ASAs should not need to be adjusted manually in service to correct excessive push rod stroke. Excessive stroke may be an indication that a problem exists with the foundation brake, automatic slack adjuster, brake actuator or other system component.

Meritor recommends that you troubleshoot the problem, replace suspect components and confirm correct brake operation before returning the vehicle to service.

Service Brake Switch Test
Effective August 11, 2008, Mack made a change to the vehicle electronic control unit (VECU) software which affects cruise control. As an added test to ensure that the service brake switch is functional, press and release the brake pedal after the engine has been started.

This simple test verifies that the service brake switch is functioning and that cruise control will deactivate when the service brakes are applied. If the brake pedal is not depressed after starting the engine, cruise control will not function.

The change affects both newly manufactured vehicles and vehicles on which the VECU has been reprogrammed.

On a limited number of chassis having a VECU which already contains software Part No. 21187006, it may be necessary to run Accessory Kit 85114485 prior to programming so that the service brake switch test feature will function. This Accessory Kit is only necessary for vehicles which already contain VECU software Part No. 21187006, but cruise control still activates even without first applying the service brakes.

PM For Hubs
Volvo advises using the following procedure when performing basic annual preventive maintenance on front hubs with unit bearings on VN Version2 670 and 780 vehicles.

1. Check the front wheel bearing with a wheel spinner and listen to the bearings during rotation. After the tire and wheel are removed, it may be necessary to rotate the hub manually. A rotation speed of 50 rpm (82 rpm maximum) is recommended. Note: Abnormal noise in the bearings is a sign of bearing wear. Hubs with worn bearings should be replaced to avoid damage to the wheel end.
2. Check the play on the front wheel bearings by using a bar as a lever to lift. The bearings normally should be pre-tensioned, therefore there should not be any noticeable play in the bearings. Do not confuse play in the wheel bearings with play in the knuckle bolt bearings. If there is play in the bearing, the bearing clearance should be checked with a dial indicator.
3. Inspect the hub cap and torque to 369 ft.-lb.

Oil Leakage
You may see oil leakage on Mack US04 MP7 engines at the cylinder head gasket joint on the left-hand side of the cylinder block between cylinders 3 and 4. This leakage results from a manufacturing defect which exists on the cylinder head capscrews (Part No. 1547419).

This defect, which is a recessed surface abnormality on the underside of the screw head approximately 0.008 inches deep, allows oil to leak into the cylinder head capscrew hole (see Figure 1).

Oil builds up in the bottom of the screw hole, migrates up the screw threads and then seeps past the cylinder head gasket, exiting the engine between the cylinder head and cylinder block joint.

If you find this type of leakage, remove the cylinder head, replace the cylinder head gasket and inspect the underside of the capscrew heads for this surface defect. If you find evidence of this defect, replace the cylinder head capscrew.

You must use a suction gun or vacuum to remove any accumulated oil from the bottom of the screw holes in the cylinder block where capscrews having the defect are located.

Remove as much oil as possible from the capscrew holes or there still may be leakage after the repair is completed.

Safety Recalls
The National Highway Traffic Safety Administration (NHTSA) has issued the following recalls:

• Insufficient torque was applied during the installation process to the nut on the pinch bolt that secures the lower steering shaft to the steering gear box on 160 model year 2008-2009 Autocar ACX, WX and WXLL Class 8 trucks. It was found that the torque controlled tool was calibrated to a lower torque rating than specified for the application. If the steering bolt were to loosen, the driver would experience loss of steering control increasing the risk of a crash.
• One hundred and three model year 2008-2009 Autocar ACX vehicles with right-hand drive fail to conform to the requirements of Federal Motor Vehicle Safety Standard No. 121, Air Brake Systems. This standard specifies performance and equipment requirements for vehicles equipped with air brake systems, including air-over-hydraulic brake systems, to ensure safe braking performance under normal and emergency conditions.
• More than 3,800 model year 2008 Hino ND8J, NE8J, NJ8J and NV8J Class 6 and 7 conventional-cab trucks equipped with J08E-TV or J08E-TW engines have an improperly shaped supply pump coupler located between the supply pump and the air compressor. The coupling may crack, the gear train and valves of the engine could break and the engine could stop running. This would disable the power steering system, stop the supply of air to the air tank and may result in insufficient braking.
• A failure of the fuel injection pump coupler can occur on 549 Nissan Diesel model year 2008 UD1800, UD2000, UD2300, UD2600 and UD3300 medium-duty trucks. The bottom corner of the notched drive surface was machined improperly. With increased fuel pump pressure, the required turning torque on the drive coupler increased. The increased turning torque could crack the coupler at the bottom corner without warning under normal operating conditions. Continued operation with a cracked drive coupler could result in the coupler breaking and causing the engine to stall and not restart.
• On 14,048 model year 2008-2010 Navistar LoneStar and ProStar trucks, the service brake air line that runs from the tractor protection valve to the fast brake module may separate from the module resulting in loss of trailer service brakes. Loss of trailer service brakes may cause a crash.

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